Set file name with auto-number

Python beginner here: I wrote a script which creates a file every 3 minutes, I used strftime to set the name according to date/time it was created:

dt = datetime.now()
dtTemp = dt.strftime('%d-%b-%Y - %H-%M-%S')
filename = '/home/pi/baby_lapse/%s.jpg' % dtTemp

Here's an example of the output:

18-Jan-2019 - 23-21-03.jpg

The problem is that once I have more than one month of files, it creates a problem to sort the files by file name, which is important to me.

To resolve it, I thought to add some auto-number before the strftime string so it will produce an output such as:

000 - 18-Jan-2019 - 23-21-03.jpg

001 - 18-Jan-2019 - 23-24-03.jpg

002 - 18-Jan-2019 - 23-27-03.jpg

How can it be achieved?

Solution

I decided to follow @chepner suggestion and used 2019-01-18 as the date format.

After setting the date format for future records, I had to run a data fix and fix the naming of the existing records.

I ended up writing my own script that converts file names from this 18-Jan-2019 - 23-21-03.jpg format to 2019-01-18 - 23-21-03.jpg, I'm sharing it in case someone has a similar scenario:

import os
Months = {
    "Jan": "01",
    "Feb": "02",
    "Mar": "03",
    "Apr": "04",
    "May": "05",
    "Jun": "06",
    "Jul": "07",
    "Aug": "08",
    "Sep": "09",
    "Oct": "10",
    "Nov": "11",
    "Dec": "12"
}

for filename in os.listdir("."):
  originalDateTime = filename.split(' ') #example: 18-Jan-2019 - 23-21-03.jpg
  date = originalDateTime[0] #18-Jan-2019
  datesplit = date.split('-') # '18', 'Jan', '2019'
  dayOfMonth = datesplit[0] #18
  month = datesplit[1] #Jan
  year = datesplit[2] #2019
  newFileName = year + '-' + Months.get(month, "none") + '-' + dayOfMonth + ' - ' + originalDateTime[2]
  print newFileName # 2019-01-18 - 23-21-03
  os.rename(filename, newFileName)